A midtown Manhattan building being demolished for a boutique hotel partially collapsed Friday, killing one construction worker and trapping another for nearly four hours until he could be rescued from the debris, officials said.

The five-story building at 27 W. 38th St. was being demolished "using partial mechanical means" when an "internal collapse" brought all five floors to the basement level, killing one construction worker, officials said. The rescued worker, who was described as "conscious and alert" by police, was pulled from the collapse and taken to Bellevue Hospital Center.

Fire Commissioner Daniel Nigro called the site that spans 25-27 W. 38th St. a "very dangerous place to work."

The FDNY responded to a call of a building collapse at the rear of the building about 10:28 a.m. More than 20 units were at the scene as surrounding streets were closed off and traffic was reduced to a crawl on Sixth Avenue as police redirected vehicles away from the area.

The FDNY requested a structural stability inspection from the Department of Buildings following the partial collapse. The Department of Buildings database says demolition began in May. A spokesman for the Department of Buildings said the agency was on the scene investigating the collapse.

The building is owned by Fortuna Realty Group LLC, which reportedly bought the property for $12 million in 2012. It is the planned site of the 27-story Aloft New York Midtown, a Starwood Hotels and Resorts property that is expected to open in fall 2016.

"We are very saddened to hear media reports of the accident, and our thoughts are with the family of the worker who was reported to have lost his life and with workers who were injured," a Starwood spokesperson said in a statement. "While this is a site for a future Aloft hotel, we are not involved at this stage and any questions should be directed to the developer, Fortuna Realty Group."

A person who answered the phone at Fortuna Realty Group said the company had no comment and referred calls to Northeast Service Interiors, a Maspeth-based demolition company. A woman who answered the phone at Northeast Service Interiors said the company had no immediate comment.

“Everybody is on site. We don't have any details,” said the woman, who would only identify herself as Meg.

There have been a number of high-profile construction-related accidents at planned midtown hotels over the last six months. In April, one person was killed in a crane accident at the future site of The Even Hotel on East 44th Street. Less than two weeks later, a construction worker fell 24 stories at the site of Riu Hotel Times Square. Just last month, a crane drill fell from the planned site of the Virgin Hotel near the corner of West 30th Street and Sixth Avenue, damaging an NYPD van.

The city has experienced a boom of hotel construction in recent years. More than 60 hotels have opened in Manhattan since 2012 and about 75 more are slated to open by 2016.

Corey Rockafeler, who works for Bell Funding Solutions at 57 W. 38th St., told amNewYork that he heard a loud crash.

He noted the frequency of citywide construction-related accidents in recent months and said the latest tragedy calls into question whether construction companies are focused on protecting people.

He wondered: How many lives will be lost before we focus on this issue?